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I'm trying to use some unusual network configurations.

Host1 (internet gateway): IP: Mask:

Host2: IP: Mask: Default gateway:

I can't ping the Host1 from Host2. Did I miss something here?

I'm using Linux Ubuntu 10.04 and the gateway is a internet router. I've tested the same scenario in another place, with every hardware different from those, and got the same results. Tested in an embedded system (linux) too, same results.

Thanks very much.

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Some more info would be useful; what's the OS of the two hosts? Might either host be using any software that might block ICMP? Can you ping in the other direction (pinging host2 from host1)? – RainyRat Sep 2 '11 at 15:59
Try setting your masks to, which should cover just the two class-c blocks you are using. – tomjedrz Sep 2 '11 at 16:07
What are the devices? I would not be at all surprised if a cheap consumer router simply can't handle a subnet bigger than a class C. – tomjedrz Sep 2 '11 at 16:08
masks didn't work. Changed in both hosts (pc and router). – Marcus Sep 2 '11 at 17:47

Did I miss something here?

Cable plugged in? Servers switched on? OS installed? :-)

No where near enough details to help sorry. What OS are you running, can you supply the output of the networking config tools (ipconfig/ifconfig/etc). Are the link-lights lit up on your NICs? Are you using a switch or crossover? etc etc etc.

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Everything set. Changing the ip and mask of Hos2 to,, it works fine. Running Linux Ubuntu 10.04 (tested on embedded linux too... same behavior). – Marcus Sep 2 '11 at 17:42

Didn't answer: Are both on the same switch/How are they physically connected?

If so, what about software firewalls?

For reference: Your network is CIDR: This encompasses: sounds theoretical... do your hosts support CIDR subnetting?

Use the IETF standard range for private Class B subnets: (at least to test).


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Looks like my Switch was doing something wrong. I'll try some more tests and will be back when I get results. Thanks for your help. – Marcus Sep 2 '11 at 20:36
Sure, i mean... that would definitely do it... just think... Ping is "sort of an application," meaning, one computer has to be able to have something living somewhere that says "oh, hey... check out this ICMP echo request... I guess I should response with an ICMP echo reply." This means, it has to traverse up the stack until it's serviced... so switches, software firewall, etc, should all be considered; just like dealing with inter-application networking. – mbrownnyc Sep 5 '11 at 14:17

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